As indicated in Patent Document 1, as a pressure sensor used in a flow rate measuring mechanism or a mass flow controller of this type, a pressure sensor is known that is configured to receive the pressure of fluid on a pressure sensing surface provided on a diaphragm or the like and to measure the fluid pressure on the basis of a positional change of the pressure sensing surface. For pressure sensors using this method, the larger the area of the pressure sensing surface of the pressure receiving member is, the higher the level of sensitivity is.
Examples of conventional mass flow controllers include one in which a pressure sensor and a flow rate adjusting valve are attached to a body that has formed therein a flow path through which a control-target fluid flows. In recent years, in particular, to meet the demand to arrange a plurality of mass flow controllers side by side in a compact manner, a mass flow controller 100′ has been developed, as illustrated in FIG. 15, so as to have an oblong body 1′, while a face thereof extending parallel to the longitudinal direction thereof is designated as a component part attachment face 1x′, so that pressure sensors 2′ and a flow rate adjusting valve 4′ are attached to the component part attachment face 1x′ in series along the longitudinal direction. The mass flow controller 100′ is designed to keep the width-direction dimension of the entire mass flow controller compact.
However, in conventional mass flow controllers, because the pressure sensors are positioned so that the pressure sensing surfaces thereof extend parallel to the component part attachment face of the body, if we try to further reduce the width-direction dimension of the entire mass flow controller, the areas of the pressure sensing surfaces become smaller, which may lead to a decrease in the sensitivity. This is a bottleneck in the endeavor to make mass flow controllers compact and, especially, to reduce the size in the width direction.
Further, in order to provide a magnetic shield for, and to provide a protection against dust for, component parts such as the pressure sensor and the flow rate controlling valve attached to the body and in order to facilitate handling of the flow rate controller, the flow rate controller is provided with a casing that houses therein component parts such as the pressure sensor and the flow rate controlling valve. To reduce the dimension of the flow rate controller in the width direction, it is necessary to reduce the dimension of the casing in the width direction, too.
To reduce the width dimension of the casing, it is possible to thin a metal plate by performing a sheet metal process, in the same manner as conventional casings have been produced. However, this method has a problem where it is difficult to achieve a sufficiently high level of precision in the processing and where the casing is easily damaged due to an insufficient mechanical strength thereof.